package com.changgou.system.util;

import io.jsonwebtoken.JwtBuilder;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.SignatureAlgorithm;

import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import java.util.Base64;
import java.util.Date;

/*
*   JWT工具类
* */
public class JwtUtil {
    //有效期为
    public static final Long JWT_TTL = 3600000L; //一个小时
    //设置密钥明文
    public static final String JWT_KEY = "itcast";

    /**
     * 创建token
     *
     * @param id
     * @param subject
     * @param ttlMillis
     * @return
     */
    public static String createJWT(String id, String subject, Long ttlMillis) {
        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
        long nowMillis = System.currentTimeMillis();
        Date now = new Date( nowMillis );
        if (ttlMillis == null) {
            ttlMillis = JwtUtil.JWT_TTL;
        }
        long expMillis = nowMillis + ttlMillis;
        Date expDate = new Date( expMillis );
        SecretKey secretKey = generalKey();

        JwtBuilder builder = Jwts.builder()
                .setId(id)                      //唯一的ID
                .setSubject(subject)            //主题  可以是JSON数据
                .setIssuer( "admin" )           //签发者
                .setIssuedAt( now )             //签发时间
                .signWith( signatureAlgorithm,secretKey ) //使用HS256对称加密算法签名，第二个参数为密钥
                .setExpiration( expDate );      //设置过期时间
        return builder.compact();
    }

    /**
     * 生成加密后的秘钥 secretKey
     * @return
     */

    private static SecretKey generalKey() {
        byte[] encodedKey = Base64.getDecoder().decode( JwtUtil.JWT_KEY );
        SecretKey key = new SecretKeySpec( encodedKey, 0, encodedKey.length, "AES" );
        return key;
    }


}
